Nested Virtualization Performance In A Computer System

Abstract

A virtualization architecture for improving the performance of nested virtualization in a computer system. A virtualization instruction reads or writes data in a control structure used by a virtual machine monitor (VMM) to maintain state on a virtual machine (VM) to support transitions between a root mode of operation of a CPU in which the VMM executes and a non-root mode of operation of the CPU in which the VM executes. A privileged data access is made to a primary control structure according to the virtualization instruction if the CPU is in the root mode. A non-privileged data access is made to a secondary control structure according to the virtualization instruction if the CPU is in the non-root mode and a secondary control structure field in the primary control structure is enabled.

Description

BACKGROUND[0001]1. Field of the Invention[0002]The present invention relates to hardware-assisted virtualization of data processing resources. More particularly, the invention concerns improvements in providing multiple layers of hardware-assisted virtualization.[0003]2. Description of the Prior Art[0004]By way of background, modern microprocessors, such as those based on the x86 architecture, include hardware-assisted support for virtualization. A set of virtualization instructions allows a hypervisor to operate in a super-privileged root mode while running guest operating systems and application software in non-root mode at their normal privilege levels. The x86 hardware virtualization feature is presently not virtualized itself. This may prevent an x86 root-mode hypervisor from efficiently running a non-root mode hypervisor as a guest, a concept known as nested or layered virtualization. The two main techniques to address this shortcoming are trap-and-emulate and dynamic translat...

AI Technical Summary

Benefits of technology

[0005]A virtualization architecture for improving the performance of nested virtualization in a computer system. A virtualization instruction reads or writes data in a control structure used by a virtual machine monitor (VMM) to maintain state on a virtual machine (VM) to support transitions between a root mode of operation of a CPU in which the VMM executes and a non-root mode of operation of the CPU in which the VM executes. A privileged data access is made to a primary control structure according to the virtualization instruction if the CPU is in the root mode. A non-privileged data access is made to a secondary control structure according to the virtualization instruction if the CPU is in the non-root mode and a secondary control structure field in the primary control structure is enabled.

Problems solved by technology

The high frequency of virtualization instructions in the critical code paths can make this mechanism prohibitively slow.

This is complicated and may have an unacceptably high performance impact on certain workloads.

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